Closure

ABSTRACT

In the case of a closure for a container having a content, in particular a bottle or the like made from plastic, glass or the like, with a cap, in particular made of plastic, for sealing connection to a neck of the container, which neck has an edge, with at least one knife edge, which is arranged around a central axis of the cap in the region of the clear width of the neck and is intended for severing a sealing foil, which is sealed onto the edge, during axial displacement of the at least one knife edge through the sealing foil, a screw cap which can be screwed onto and can be unscrewed from the cap is provided, during the screwing-on of which the at least one knife edge can be displaced in the direction of the sealing foil, wherein this screw cap has an initial screwing position, in which the sealing foil is still undamaged, and, after further screwing, an end-stop screwing position, in which the sealing foil is pierced by the at least one knife edge. The screw cap has a pouring and/or drinking opening in the manner of a sports cap. An axial plunger which has the at least one knife edge is arranged centrally between the cap and the screw cap and is guided displaceably in a coaxial guide of the transverse wall of the cap.

The invention relates to a closure for a container having contents, particularly a bottle or the like made from plastics material, glass or the like, comprising a cap, particularly made from plastics material, to be sealingly connected to a neck of the container, which neck has a rim, further comprising at least one knife edge disposed around a center axis of the cap in the region of the inside width (D) of the neck for the purpose of severing a sealing film or foil sealingly attached to said rim when the at least one knife edge is axially displaced through the sealing film or foil, further comprising a concentric union possessing a male thread and situated on an upper transverse wall of the cap, and a screw cap capable of being screwed down onto, and unscrewed up from, said thread, the screw cap having at least one actuator element positioned at the inner surface of the cover of the cap by which during screwing the cap down onto the union the at least one knife edge can be displaced toward the sealing film or foil, this screw cap having an initial screwing position, in which the sealing film or foil is still intact, and, after continued screwing, a final screwed position, in which the sealing film or foil has been pierced by the at least one knife edge.

A closure of this type is disclosed in the printed publication WO 2004/113184 A2, which closure after opening of the sealing film or foil and release of a constituent to be mixed with the contents of the container, which constituent is provided with this prior art, must be completely, i.e. the cap together with the screw cap, unscrewed from the neck of the container if one wants to use some of the contents of the container. If one wishes to close again the container after having taken a part of the contents thereof, then the closure in its entirety must be screwed onto again. Hence, during unscrewing, withdrawal of contents of the container, e.g. by drinking from a bottle if the contents is a beverage, and again screwing of the closure onto the neck for the purpose of closing the container or the bottle, resp., the user needs both hands while by the separation of the closure from the container or the bottle, resp., the danger is always present anyway that the closure could fall from the hands of the user or drinker, resp.

Further there are known closures as so-called Sportscaps which for the tapping of contents of the container must be unscrewed partially only so that they can remain on the neck of the container or bottle, resp., because such a sportscap comprises a withdrawal opening which is opened even on partial unscrewing and can be closed again by screwing onto again. Sportscaps of this type enable sportsmen, especially pedal cyclists, to drink during execution of their sport without being bound to use both hands and without running a risk to possibly lose the closure. But these sportscaps can not be used with containers or bottles, resp., which are closed by a sealing film or foil because they can not provide access to the contents of the container.

The object underlying the invention is thus to provide a closure of the type mentioned above, which is formed such that it is capable of performing the functions of a Sportscap also with containers or bottles, resp., which are closed by a sealing film or foil.

This object is achieved according to the invention in that

-   a) the cap remains permanently on the neck of the container after     having been sealingly connected to the neck, that -   b) the screw cap has a decanting and/or drinking opening in the     manner of a Sportscap, that -   c) an axial piston is disposed centrally between the cap and the     screw cap and bears against an axial inner surface of the cap and is     guided for displacement in a coaxial guide in the transverse wall of     the cap, which piston possesses the at least one knife edge and is     adapted firstly to seal the screw cap against the cap by bearing     against the same, and secondly to concentrically shift, during its     displacement, the at least one knife edge to a final position toward     the sealing film or foil for the purpose of piercing the latter, and     in this final position the sealing film or foil will have been     pierced and a passageway opened between the piston and the cap, that -   d) the covering inside surface of the screw cap and the end face of     the piston opposite thereto together comprise an actuator in the     form of a concentric connecting pair composed of a plunger and a     counterpart mating therewith, the plunger and its counterpart     interengaging such that they cannot be displaced axially relative to     each other and are axially positioned such that on said continued     screwing of the screw cap to its final screwed position, the     container's contents can have access to the screw cap and its     decanting and/or drinking opening by way of the piston, which can be     displaced toward the sealing film or foil, on continued screwing of     the screw cap, thereby breaking the seal firstly between the piston     and the cap, and secondly between the piston and the screw cap,     while the knife edge disposed on the piston pierces the sealing film     or foil, and that -   e) when the screw cap is screwed in the reverse direction and thus     back to its initial position, the piston can again be caused to     sealingly bear against the cap such that the passageway to the screw     cap and its decanting opening is again blocked.

The sealing connection of the cap with the neck of the container can be effected in various ways, e.g. by welding or gluing, etc. But it is most common to design the cap as a first screw cap, so that the aforementioned screw cap becomes the second screw cap. The difference consists in the fact that with the pertinent prior art as acknowledged this first screw cap and thereby the entire closure must be screwed off if one will get access to the contents of the container, whereas with the subject matter of the invention the cap after having sealingly mounted same to the neck can remain permanently thereon, even also if it is shaped as a first screw cap. If it is welded or otherwise bonded thereto, the permanent connection is understood a priori.

The closure of the invention is therefore preferably designed such that the cap, as a first screw cap, comprises a sleeve section comprising a female thread adapted for screwing onto a male thread on a container neck comprising a rim, and the screw cap is designed as a second screw cap.

The invention thus particularly relates to a screw closure comprising a first screw cap, which is particularly made of plastics material, and has a sleeve section which comprises a female thread adapted for screwing onto a male thread on the neck of a container, particularly a bottle or the like having contents and made of plastics material, glass or the like, which neck comprises a rim, and comprises at least one knife edge disposed in the region of the inside width of the neck and adapted for piercing a sealing film or foil sealingly affixed to the rim when the at least one knife edge is axially displaced through the sealing film or foil, further comprising a concentric union, which comprises a male thread and is disposed on an upper transverse wall of the first screw cap, and a second screw cap, which can be screwed down onto, and unscrewed up from, the first screw cap, the second screw cap having at least one actuator element positioned at an inner side of a cover of the said second screw cap, it being possible by this actuator element to displace the at least one knife edge toward the sealing film or foil when the second screw cap is being screwed onto the union, this second screw cap having an initial screwing position, in which the sealing film or foil has not yet been pierced, and a final screwed position, in which the sealing film or foil has been pierced by the at least one knife edge.

Starting with this embodiment of the screw closure the said object is met in that

-   a) the first screw cap remains permanently on the neck of the bottle     after having been screwed onto the neck, that -   b) the second screw cap has a decanting and/or drinking opening in     the manner of a sportscap, that -   c) an axial piston is disposed centrally between the cap and the     screw cap and bears against an axial inner surface of the cap and is     guided for displacement in a coaxial guide in the transverse wall of     the cap, which piston possesses the at least one knife edge and is     adapted firstly to seal the screw cap against the cap by bearing     against the same, and secondly to concentrically shift, during its     displacement, the at least one knife edge to a final position toward     the sealing film or foil for the purpose of piercing the latter, and     in this final position the sealing film or foil will have been     pierced and a passageway opened between the piston and the cap, that -   d) the covering inside surface of the screw cap and the end face of     the piston opposite thereto together comprise an actuator in the     form of a concentric connecting pair composed of a plunger and a     counterpart mating therewith, the plunger and its counterpart     interengaging such that they cannot be displaced axially relative to     each other and are axially positioned such that on said continued     screwing of the screw cap to its final screwed position, the     container's contents can have access to the screw cap and its     decanting and/or drinking opening by way of the piston, which can be     displaced toward the sealing film or foil, on continued screwing of     the screw cap, thereby breaking the seal firstly between the piston     and the cap, and secondly between the piston and the screw cap,     while the knife edge disposed on the piston pierces the sealing film     or foil, and that -   e) when the screw cap is screwed in the reverse direction and thus     back to its initial position, the piston can again be caused to     sealingly bear against the cap such that the passageway to the screw     cap and its decanting opening is again blocked.

By the invention it is achieved that for withdrawal of at least a part of the contents of the container it is not necessary to remove the closure in its entirety from the neck and to replace it onerously for sealingly closing the container anew. To the contrary, it is sufficient to loosen or partially unscrewing, resp., of the screw cap or second screw cap in order to make decanting or drinking of the contents of the container possible. This is particularly advantageous when using bottles containing foodstuffs or beverages during sporting activities, e.g. cycling, but it is to be understood that the invention is not restricted to containers for beverages or foodstuffs.

First the neck of the container is hermetically closed by the sealing film or foil which has been sealed onto a circular ring shaped sealing surface of the edge of the neck.

It is particularly advantageous if the male thread on the central union forms a quick thread with the thread of the second screw cap such that less than one complete turn is required in order to open the container in one direction of rotation or to close the container in the reverse direction of rotation. This makes it even easier for the user to hold the container or bottle in one hand and use the thumb and index finger of the same hand to open and close the second screw cap.

It has proven useful to arrange the plunger on the inside surface of the second screw cap and the coupling sleeve on the side of the piston opposite thereto.

According to a preferred embodiment, the plunger can be snapped into the coupling sleeve such that the former can be rotated, but not displaced axially therein. However, it is clear that a suitable thread pair can optionally be provided between the plunger and the coupling sleeve, which thread pair contributes to the amount of displacement of the coupling sleeve relatively to the first screw cap when the second screw cap is screwed.

On the other hand, it may also be sufficient to connect the plunger and the coupling sleeve by a force fit. However, if a thread pair is provided, then a right-hand thread pair would be to be preferred for the purpose of increasing the amount of displacement.

The piston is advantageously a substantially flat disc with a coaxial stub which forms the coupling sleeve and the outer circumference of which represents, together with a coaxial passageway of corresponding width in the transverse wall of the first screw cap, the coaxial guide forming a seal between the piston and the first screw cap in the initial screwing position of the second screw cap.

It has proven to be advantageous to provide one or more seals on the upper side of the piston, which seals can each be caused to bear against the first screw cap in the form of annular gaskets.

The passageway can be formed by notches provided at intervals along the periphery of the stub, which notches reach the region of the coaxial guide and thus mate with the wall of the coaxial through opening of the first screw cap only when the second screw cap approaches its final screwed position.

Above its female thread adapted for screwing onto the male thread on the neck of the container, the first screw cap advisably comprises a first encircling flexible sealing lip adapted to bear against a radial part of the rim of the neck sealed by the sealing film or foil.

Above its female thread adapted for screwing onto the male thread on the neck of the container, the first screw cap can further comprise a second sealing lip disposed between the first flexible sealing lip and the sleeve section.

This second sealing lip can be advantageously expanded by said rim when the first screw cap is screwed onto the container for the purpose of remaining thereon and can then be clamped between said rim and the wall of the first screw cap, thereby providing a particularly effective and durable seal between the neck and the first screw cap.

Finally, the second screw cap can comprise an inner collar, which remains inside the union of the first screw cap after the second screw cap has been screwed onto the first screw cap and the outside surface of which has at least one encircling sealing lip for creating a seal against the inside surface of the union.

The second screw cap and the union can preferably have a left-hand thread pair. This has the advantage that a left-hand turn of the second screw cap causes opening of the container or bottle, and a right-hand turn closes it, these being operations to which the consumer is accustomed. Unfamiliar to the consumer is only that when the container is opened, the second screw cap is screwed onto the union and when it is closed, the second screw cap is partially unscrewed from the union of the first screw cap.

The invention and its preferred embodiments are explained in more detail below with reference to an exemplary embodiment shown in the figures of the drawings, in which:

FIG. 1 is a side view, partial cut away, of a closure of the invention in the form of a screw-closure variant, in its initial screwing position;

FIG. 2 shows, on an enlarged scale, a detail of FIG. 1;

FIG. 3 is a side view, corresponding to FIG. 1, of the closure in its final screwed position, in which the sealing film or foil has been pierced;

FIG. 4 is a side view, corresponding to FIG. 1 and FIG. 2, of the closure after the second screw cap has returned to its initial screwing position;

FIG. 5 is a perspective exploded view, as seen obliquely from below, of the closure according to the preceding figures;

FIG. 6 is a plan view of the underside of the piston.

FIGS. 1, 3, and 4 show a closure 1 comprising a first screw cap 2, which is made, in particular, of plastics material and has a sleeve section 4 provided with a female thread 3 adapted to screw onto a male thread 5 on a neck 7 of a container 9, in particular a bottle or the like, made of plastics material, glass or the like and having contents 8, which neck 7 comprises a rim 6. This first screw cap 2 comprises a so-called tamper-evident closure 4′ at the free end of its sleeve section 4. The tamper-evident closure 4′ snaps onto the neck 7 and would tear off if the first screw cap 2 were unscrewed again, which should normally not take place.

Further there are provided a concentric union 17 which comprises a male thread 16 and is disposed on an upper transverse wall 18 of the first screw cap 2, and a second screw cap 19 which can be screwed down onto, and unscrewed up from, the first screw cap 2 by means of a female thread 33, the second screw cap 19 having at least one actuator element 21 positioned on its covering inside surface 20, it being possible by this actuator element 21 to displace the at least one knife edge 11 toward the sealing film or foil 12 when the second screw cap 19 is being screwed onto the union 17, this second screw cap 19 having an initial screwing position shown in FIG. 1, in which the sealing film or foil 12 has not yet been pierced, and after continued screwing in the direction of arrow A, a final screwed position shown in FIG. 3, in which the sealing film or foil 12 has been pierced by the at least one knife edge 11.

According to the invention the first screw cap 2 now remains permanently on the neck 7 of the bottle 9 after it has been screwed on. The second screw cap 19 comprises a decanting and/or drinking opening 22 of the sportscap type; an axial piston 25 bearing against the axial inside surface 24 of the first screw cap 2 is disposed centrally relative to the first screw cap 2 and the second screw cap 19 and is guided for displacement in a coaxial guide 26 in the transverse wall 18 of the first screw cap 2, which piston 25 possesses the at least one knife edge 11. This piston 25 is adapted firstly to seal the second screw cap 19 against the first screw cap 2 by bearing against the latter and secondly to shift the at least one knife edge 11 to a final screwed position (FIG. 3) during the displacement of the piston in the direction of arrow A toward the sealing film or foil 12 for the purpose of piercing the latter. The sealing film or foil 12 will have been pierced in this final screwed position and a passageway 27 opened between the piston 25 and the screw cap 2;

the covering inside surface 20 of the second screw cap 19 and the end face 28 of the piston 25 opposite thereto together comprise a concentric connecting pair as actuator element 21. The connecting pair is composed of a plunger 29 and a counterpart 30 mating therewith. The plunger 29 and the counterpart 30 interengage such that they cannot be displaced axially, but in this version can be rotated, and are positioned relatively to each such that when the second screw cap 19 is screwed down to its final screwed position shown in FIG. 3, the bottle's contents 8 are released to flow toward the second screw cap 19 and its decanting and/or drinking opening 22 by way of the piston 25, which is to be displaced, when the second screw cap is further screwed down, in the direction of arrow A toward the sealing film or foil 12 and breaks the seal firstly between it and the first screw cap 2 and secondly between it and the second screw cap 19, during which movement the knife edge 11 disposed on the piston 25 pierces the sealing film or foil 12; when the second screw cap 19 is screwed in the reverse direction (direction of arrow B, FIG. 4) and thus back to its initial position shown in FIG. 1, the piston 25 can again be caused to sealingly bear against the first screw cap 2 such that the flow of the contents toward the second screw cap 19 and its decanting opening 22 is again blocked. The neck 7 of the container 9 is initially sealed hermetically by means of the sealing film or foil 12, which is sealingly affixed to an annular sealing surface 32 (FIG. 2) of the rim 6 of the neck 7. It is obvious that the knife edge 11 will have to have pierced the sealing film or foil 12, as clearly shown in FIG. 3 and FIG. 4, if the container's contents 8 are to be released.

The at least one knife edge 11 is formed on the piston 25.

In the embodiment shown four knife edges 11 are disposed at the periphery of the piston 25 at intervals of 90° relative to each other. However, it is obvious that other numbers, including odd numbers, of knife edges 11 can be provided.

In the present case, each knife edge 11 is provided on a pipe section 51, which is disposed substantially parallel to the longitudinal axis 50 of the closure 1 on the periphery of the piston 25 and is open at both ends and extends with its knife edge 11 directed toward the sealing film or foil 12 beyond the underside 52 of the piston 25.

In the embodiment shown, each knife edge 11 is formed by that end face 53 of each pipe section 51 that faces the sealing film or foil 12, said end face 53 being slanted in relation to the longitudinal axis 50.

Advantageously, the slope of the end face 53 of a pipe section 51 is steepest relative to the longitudinal axis 50 in the region of that portion thereof which is nearest to said sealing film or foil 12. The knife edge 11 is formed along this steepest portion, while the opposite portion of the end face 53 is flatter with the result that when the end face 53 passes through the sealing film or foil 12, the latter is pierced only partially, forming a partially severed flap of material 56, which has been pushed down in the direction of arrow A (FIG. 3).

The fact that the end face 53 and thus also the region of the pipe section 51 adjoining the end face 53 pass through the sealing film or foil 12, ensures that the flaps 56 formed from the sealing film or foil 12 will not bend back to reseal the opening formed for the passage of the container's contents.

In the preferred embodiment illustrated, the opposite part of the end face 53 is that radially inner part of the end face that is nearest to the longitudinal axis 50 and has no severing function. Furthermore, the entire end face 53 has a concave form in this embodiment.

In order to ensure that the partially severed flap of material 56 is folded away securely, a pressure bead 55 is provided (cf. FIGS. 3 and 6) on that opposite part of the end face 53 that has no severing function. This pressure bead 55 ensures that the respective flap of material 56 is bent down gently.

The male thread 16 on the central union 17 advantageously forms, together with the female thread 33 on the second screw cap 19, a quick thread such that less than one complete turn is required to open the container 9 in one direction of rotation or to close it in the reverse direction of rotation.

In the embodiment illustrated, the plunger 29 is disposed centrally on the inside surface of the second screw cap 19 and its counterpart, the coupling sleeve 30, is disposed centrally on the opposite side of the piston 25.

The plunger 29 can snap into the coupling sleeve 30 such that it can be rotated but not be displaced axially therein, cf. catch 54.

Alternatively, the plunger 29 and the coupling sleeve 30 may be mutually force-fitted such that the plunger 29 rotatably entrains the coupling sleeve 30 and thus the piston 25 and each knife edge 11 pierces the sealing film or foil 12 on a circular path.

It would also be possible to provide the plunger 29 and the coupling sleeve 30 with a thread pair.

The piston 25 is advantageously a flat disc with a coaxial stub forming the coupling sleeve 30, while the outer periphery of which represents, together with a coaxial through opening of appropriate diameter and located in the transverse wall 18 of the first screw cap 2, the coaxial guide 26, which forms a seal (sloping surfaces 31) between the piston 25 and the first screw cap 2 in the initial screwing position of the second screw cap 19.

On the top surface, i.e. the end face 28, of the piston 25, only one further seal is provided in this case, which seal can be in the form of an annular gasket 36 bearing against a corresponding annular groove in the first screw cap 2.

Several such gaskets may be present, depending on requirements and on the container's contents.

The passageway 27 is formed by notches 41 provided at intervals along the periphery of a shoulder of the coupling sleeve, which in this case forms the counterpart 30. These notches 41 reach the region of the coaxial guide 26 and thus come to mate with the wall of the coaxial through opening of the first screw cap 2 only when the second screw cap 19 approaches its final screwed position shown in FIG. 3.

Above its female thread 3 adapted to screw onto the male thread 5 on the neck 7 of the container 9, the first screw cap 2 comprises a first encircling flexible sealing lip 42 for bearing against the radial part of the rim 6 of the neck 7, which had been initially sealed by the sealing film or foil 12.

Above its female thread 3 adapted to screw onto the male thread 5 on the neck 7 of the container 9, the first screw cap 2 advantageously comprises a second sealing lip 43 disposed between the first flexible sealing lip 42 and the sleeve section 4. This second sealing lip 43 can be expanded by the rim 6 when the first screw cap 2 is screwed onto the container 9 for the purpose of remaining thereon and can then be clamped between the rim 6 and the wall of the first screw cap 2.

The second screw cap 19 comprises an inner collar 44, which remains inside the union 17 of the first screw cap 2 after the second screw cap has been screwed onto the latter and the outside surface of which has at least one encircling sealing lip 45 for the purpose of providing a seal against the inside surface 46 of the union 17.

The second screw cap 19 and the union 17 advantageously form a left-hand thread pair 16, 33, since a screw cap of, say, a drinking bottle is usually opened by a turn to the left.

The closure functions as follows:

A transparent safety cap 48 present here as shown in FIG. 1 and preferably made of plastics material is first torn off. To open the container or bottle 9, the second screw cap 19 is screwed to the left until it reaches the stop 49 shown in FIG. 3. By means of the plunger 29 and the coupling sleeve 30, the piston 25 is moved into the opening position shown in FIG. 3. The knife edges 11 will then have pierced the sealing film or foil 12. A radial inner rim 55 (here in the form of a pressure bead) of the respective pipe section 51 will have pressed a resulting cut-out flap 56 of the sealing film or foil downwardly (FIG. 3), creating corresponding holes so that the container's contents 8 can pass through the pipe sections 51 and, possibly, between the pipe sections 51 and the holes thus created. This causes a pressure relief in the space between the piston 25 and the first screw cap 2 causing local turbulence of the discharged contents of the container, without the latter squirting through the opening 22 of the closure 1 of the invention into the environment and possibly into the consumer's face. This is particularly advantageous, for example, in the case of carbonated beverages. The container's contents 8 can then flow past the sloping surfaces 31, 31 a (FIG. 3 and FIG. 4), which have moved apart from each other, through the passageway 27 formed by the notches 41 and then through the decanting and/or drinking opening 22.

In order to re-close the container or bottle 9, the second screw cap 19 will be screwed back to the right to its initial position, cf. FIG. 4, the piston 25 being entrained to again bear sealingly against the inside surface 24 of the first screw cap 2. The notches 41 will also move upwardly and the sloping surfaces 31, 31 a will again bear against each other such that the previously opened passageway 27 (FIG. 3) in the guide 26 will be re-closed. 

1. A closure for a container having contents, particularly a bottle or the like made from plastics material, glass or the like, comprising a cap, particularly made from plastics material, to be sealingly connected to a neck of said container, which neck has a rim, further comprising at least one knife edge disposed around a center axis of said cap in the region of the inside width of said neck for the purpose of severing a sealing film or foil sealingly attached to said rim when said at least one knife edge is axially displaced through said sealing film or foil, and further comprising a concentric union possessing a male thread and situated on an upper transverse wall of said cap, and a screw cap capable of being screwed down onto, and unscrewed up from, said thread, the screw cap having at least one actuator element positioned at the inner surface of the cover of the cap by which during screwing the cap down onto the union the at least one knife edge can be displaced toward the sealing film or foil, this screw cap having an initial screwing position, in which the sealing film or foil is still intact, and, after continued screwing, a final screwed position, in which the sealing film or foil has been pierced by the at least one knife edge, characterized in that the cap remains permanently on the neck of the container after having been sealingly connected to the neck, that the screw cap has a decanting and/or drinking opening in the manner of a Sportscap, that an axial piston is disposed centrically between said cap and said screw cap and bears against an axial inner surface of said cap and is guided for displacement in a coaxial guide in the transverse wall of said cap, which piston possesses the at least one knife edge and is adapted firstly to seal said screw cap against said cap by bearing against the same and secondly to concentrically shift, during displacement thereof, said at least one knife edge to a final screwed position toward said sealing film or foil for the purpose of piercing the same, and in this final screwed position the sealing film or foil has been pierced and a passageway has been opened between said piston and said cap, that both said screw cap, on its inside surface, and said piston, on its end face opposite thereto, comprise an actuator in the form of a concentric connecting pair consisting of a plunger and a mating counterpart, which interengage axially nondisplaceable, and said plunger and its counterpart are positioned relative to each other such that on said continued screwing of said screw cap to its final screwed position, the contents of said container have access to said screw cap and its decanting and/or drinking opening by way of said piston which can be moved, during said continued screwing, toward said sealing film or foil to break the seal between it and said cap, during which movement the knife edge disposed on said piston pierces said sealing film or foil, and that by screwing said screw cap in the reverse direction back to its initial position, said piston can be moved back so as to sealingly bear against said cap such that the passageway to the screw cap and its decanting opening is again blocked.
 2. The closure according to claim 1, characterized in that said cap possesses, as a first screw cap, a sleeve section provided with a female thread for screwing onto a male thread of a neck of said container, which neck has a rim and said screw cap forms a second screw cap.
 3. The closure according to claim 1, characterized in that said neck of said container is initially hermetically sealed by means of said sealing film or foil sealingly attached to an annular sealing surface of said rim of said neck.
 4. The closure according to claim 1, characterized in that said at least one knife edge is formed on said piston.
 5. The closure according to claim 1, characterized in that four knife edges are disposed along the periphery of said piston at intervals of 90°.
 6. The closure according to claim 1, characterized in that the knife edge is provided on a tube section disposed substantially parallel to the longitudinal axis of said closure at the periphery of said piston, which tube section is open at both ends and projects with its knife edge directed toward said sealing film or foil beyond the underside of said piston.
 7. The closure according to claim 6, characterized in that each knife edge is formed by a portion of the undersurface of each tube section facing a sealing film or foil, which portion is slanted relatively to the longitudinal axis.
 8. The closure according to claim 7, characterized in that said undersurface of a tube section is most steeply slanted relatively to the longitudinal axis in that region thereof which is nearest to said sealing film or foil, and the knife edge is formed on this steepest portion, while said undersurface is less steeply formed in its opposing region such that when said undersurface pierces said sealing film or foil the latter is only partially severed and forms only a partially separated flap of material which is bent down in the direction of arrow A.
 9. The closure according to claim 8, characterized in that said opposing portion of said undersurface is that radially inner part which is near to the longitudinal axis.
 10. The closure according to claim 8, characterized in that said undersurface is concave.
 11. The closure according to claim 8, characterized in that to ensure that said partially separated flap of material turns down correctly, a pressure bead is provided on said opposing portion of said undersurface.
 12. The closure according to claim 1, characterized in that said male thread of said central union forms a quick thread with the thread of said second screw cap such that less than one turn is necessary to open said container in one direction of rotation or to close it in the reverse direction of rotation.
 13. The closure according to claim 1, characterized in that said plunger is disposed centrally on the inside of said second screw cap and its counterpart formed as a coupling sleeve centrally on the opposite side of said piston.
 14. The closure according to claim 13, characterized in that said plunger can be rotatably, but not axially displaceable, locked in said coupling sleeve.
 15. The closure according to claim 13, characterized in that said plunger and said coupling sleeve are mutually force-fitted.
 16. The closure according to claim 13, characterized in that said plunger and said coupling sleeve comprise a thread pair.
 17. The closure according to claim 1, characterized in that said piston is a substantially flat disk having a coaxial rod stub forming a boss whose outside diameter corresponds to the diameter of a coaxial through opening in the transverse wall of said first screw cap to provide said coaxial guide forming a seal between said piston and said first screw cap in the initial screwing position of said second screw cap.
 18. The closure according to claim 17, characterized in that on the top side of said piston one or more further seals are provided, each of which can be caused to bear against said first screw cap in the form of an annular gasket.
 19. The closure according to claim 1, characterized in that said passageway is formed by notches which are provided at intervals at the periphery of the shoulder of said boss and which move into the region of the coaxial guide and thus for mating with the wall of the coaxial through opening of said first screw cap only when said second screw cap approaches its final screwed position.
 20. The closure according to claim 1, that characterized in that said first screw cap has a first encircling flexible sealing lip above its female thread adapted for screwing onto said male thread on said neck of said container, which sealing lip is adapted to bear axially against the radial part of said edge of said neck sealed by said sealing film or foil.
 21. The closure according to claim 20, characterized in that said first screw cap has, above its female thread adapted for screwing onto said male thread of said neck of said container, a second sealing lip disposed between said first, flexible sealing lip and said sleeve section.
 22. The closure according to claim 21, characterized in that when said first screw cap is screwed onto said container for the purpose of remaining thereon, said second sealing lip can be expanded by said rim and then clamped between said rim and the wall of said first screw cap.
 23. The closure according to claim 1, characterized in that said second screw cap has an inner collar, which remains within said union of said first screw cap after said second screw cap has been screwed onto the latter, and possesses at least one encircling sealing lip on its outside surface to create a seal against said inside wall of said union.
 24. The closure according to claim 1, characterized in that said second screw cap and said union comprise a left-hand thread pair. 